Centrifugal clutch

ABSTRACT

A slip clutch having a drum secured to the driven shaft is driven by an externally powered carrier. The carrier is supported on bearings and turns freely about the shaft. The carrier supports a pair of drive shoes secured together by springs which tend to prevent the shoes from engaging the drum. Means are provided for adjusting the mass of each drive shoe from the exterior of the drum to enable adjustment of the centrifugal force acting upon each shoe as it and the carrier are rotated. By this means, the rotational speed at which clutch engagement occurs, is made selectively adjustable.

[451 Aug. 29, 1972 Primary Examiner-Benjamin W. Wyche AssistantExaminerRa.ndall Heald Attorney-Jacque L. Meister ABSTRACT A slip clutchhaving a drum secured to the driven shaft is driven by an externallypowered carrier. The carrier is supported on bearings and turns freelyabout the shaft. The carrier supports a pair of drive shoes securedtogether by springs which tend to prevent the shoes from engaging thedrum. Means are provided for adjusting the mass of each drive shoe fromthe exterior of the drum to enable adjustment of the centrifugal forceacting upon each shoe as it and the car- Roy H. Bystrom, 6115 N.Ravenswood, Chicago, 111. 60625 Sept. 16, 1970 .192/105 A, 192/103 B,192/105 BA .Fl6d 43/24 Fi d2S4 h:-.--- 192/105 5 9 B2710 A 7 1921105 CDReferences Cited UNITED STATES PATENTS United States Patent Bystrom [54]CENTRIFUGAL CLUTCH [72] Inventor:

[22] Filed:

[21] Appl. No.: 72,679

[52] US. Cl.

[51] Int. L 1

rier are rotated. By this means, the rotational speed at which clutchengagement occurs, is made selectively 5 Claims, 3 Drawing figures m b at .m a M r ABAMA 5 5 5 0 050 H N 2 2fl2 9 9 9 u u u m J m a n a mam Hewflm kmm m r a m um. CBF a 60290 35365 99999 11111 74588 27345 77695 3,99 8 9 7 56 22 32 PATENTEU M1 2 I SHEET 1 BF PATENTEDA B 912 3.687.254

SHEET 2 OF 2 INVENTOR.

ATTY.

1 CENTRIFUGAL CLUTCH BACKGROUND OF THE INVENTION The field of theinvention is generally that of centrifugal clutches and moreparticularly is improvements in centrifugal clutches to facilitateadjustment of the speed at which the clutch engages.

There exist today, a large number of applications where small enginesprovide motive power to the driven device. In these devices it isnecessary that the load be disengaged during engine start-up and whilewarming up or idling. Mechanical centrifugal clutches or fluid couplingsare most often used to accomplish this selective disengagement whenautomatic operation is desired. However, both of these devices areeither very difficult or impossible to adjust with respect to the pointof engagement and additionally, the fluid couplings even at high inputspeed havesome slip. In many applications this inability to readilyadjust the engagement point is a serious disadvantage since itnecessarily results in performance compromises in the using device.While in some applications these compromises may not be a seriousdetriment, in others where maximum performance is necessary, theperformance compromises of conventional centrifugal clutches make themtotally unacceptable. Among the applications requiring maximumperformance are those involving racing vehicles such as go-karts andvarious cycles.

SUMMARY OF THE INVENTION It is accordingly an object of the invention toprovide a reliable centrifugal clutch which overcomes the above notedlimitations of the prior art and whose engagement speed is preciselyadjustable. It is a principal object of the invention that the means foradjusting the engagement speed be easily accessible from the exterior ofthe clutch without any need to disassemble the clutch to effect theadjustment.

These and other objects of the invention are achieved by having anoutput drum affixed to the driven member. The driving member of theclutch is a carrier having one or more friction members arranged to moveoutward to engage the drum interior under the impetus of centrifugalforce. Except when the friction members engage the drum, there is noconnection between the carrier and drum and the carrier then rotatesfreely within and coaxially with the drum. Means are provided foradjusting the mass of the friction members without disassembling theclutch.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view of the clutch ofthe invention;

FIG. 2 is a vertical section through FIG. 1 taken substantially alongline 2-2 therein and at an enlarged scale relative thereto; and

FIG. 3 is an enlarged view of one of the friction members shown in FIG.2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the clutch is shownassembled to the driven shaft 10. Drum 12 with its integral hub 14 issecured to shaft by any suitable fastener such as the taper pin 16 thatis shown. Carrier 18 is assembled coaxially the shaft 10 on bearings 24(FIG. 2) for free rotation thereabout. Collar 20 secures the carrierfrom lateral movement along shaft 10 while thrust washers (not shown)assembled between the hub 14 of the drum and the hub 28 of the carriercontrol clearance between the two. Collar 20 is secured in position onshaft 10 by means of set screw 26. This system for controlling clutchend play is preferred for its adaptability to various application.However, when large volume usage of a single application occurs, forcost reasons preferred construction then substitutes a groove in theshaft 10 plus use of various thickness retaining rings for use in placeof the collar 20.

Driving power is applied to the clutch from any suitable external powersource such as an internal combustion engine. In the embodiment of FIG.1, a sprocket 22 is provided to enable connection to such an engine.Manifestly however, any other suitable connecting means including apulley could be used without affecting the clutch itself. In still otherapplications, the carrier is directly driven by the engine and powertake off is from the shaft 10.

In FIG. 2 the carrier, together ,with friction members and associatedparts are shown in enlarged scale in a view taken along section 2-2 ofFIG. 1. Carrier 18 is generally disc-like and is possessed ofconsiderable strength to enable efficient power transmission withoutbuckling. Upstanding from the disc are various structural features usedto permit clutch operation. Among these are hub 28 into which bearing 24is pressed to enable free rotation of the carrier about shaft 10.Strengthening ribs 30 and 32 are also an integral part of the carrierand by slotting their ends as indicated at 34, are made to perform theadditional function ofguiding friction members 36 and 36' as theyalternately move inward toward the hub and outward toward the drum.Obviously, other guide means such as clips or slots in the centered hubor even no guide means can be used in place of slots 34. Secured tocarrier 18 are two stops 40 and 40' whose purpose will be made moreclear in discussion which follows. Thus far, either steel or clothfilled melamines have proven to be the best materials for the stopssince their impact resistance is great; they can have a low coefficientof friction and they wear well without galling.

As shown, two friction members 36 and 36 are used in the preferredembodiment. The two members are identical and are shown in greaterdetail in FIG. 3. As shown, member 36 is assembled into the slot 34 inrib 30 and member 36' into the slot 34' in rib 32. The two members areretained in position by tension springs 38 and 38 which are as nearlyidentical as possible. The twin extension springs tend to hold thefriction members against the stops 40 and 40' and away from contact withthe drum 12. While the springs 38 and 38' are shown connected betweenthe friction members, in certain embodiments (not shown), the springsare fastened to anchors on the carrier, instead.

The friction members 36 and 36' comprise an arcuate support member 42having an upturned flange 44 to the mass of the friction members withoutdisassembly of the clutch. As is well-known, the centrifugal forcetending to urge the friction members outward, is directly proportionalto their mass. Thus, increasing the mass will increase the centrifugalforce acting at any given angular speed and hence decrease the angularspeed at which clutch engagement will occur. The effect is identical butopposite for decreasing mass.

To achieve the adjustable mass, there is provided an arcuate shaped tube52 whose maximum radius is chosen to place the tube as far outwardly aspossible and preferably against upturned flange 44. The tube is closedat one end 62 as by soldering or by deforming and is secured to supportmember 42 as by brazing. The opposite end of the tube is provided with aright angle fitting 54 in such a manner that internal tube diameter isnot constricted. The outermost edge of fitting 54 is internally tappedfor a set screw 56 and extends outwardly to the wear limit of facingmaterial 46. As shown in both FIG. 1 and 2, an access hole 58 isprovided in the annular flange 60 of drum 12. This hole is positionedlaterally on the flange to enable its alignment with set screw 56. Thus,the screw 56 can be brought into alignment with the hole 58, the screwremoved and weights in the form of slugs or BB s added or removed, allwithout disassembly of the clutch.

In operation, as carrier 18 increases in speed, the BBs in each tubetend to cluster at the trailing edge of each tube. With the mass thusnon-uniformly distributed, the end of the friction member with the massconcentration will be the first to contact the drum. This partialengagement yields smooth pick-up of the load. As rotational speedcontinues to increase, the amount of friction material area in contactwith the drum also increases. Finally when all of the available frictionmaterial is in contact with the drum, the BBs in the tube tend to centerthemselves at the point of maximum tube radius. in certain embodimentsit has been desirable to improve distribution of the weights in the tubeduring acceleration of the clutch, usually for the purpose of minimizingfriction between the support member 42 and stops 40 and 40'. in thiscase, the tube 52, is constructed with a slightly smaller radius thanthe internal radius of flange 44, and the center of the tube is securedagainst the flange and with each end disposed proportionally radiallyinward.

When the primary consideration is maximizing transmitted torque andminimizing wear of the facing material 46 instead of smooth loadpick-up, the tube 52 is maintained substantially full. In this case massadjustments are made by increasing or decreasing the quantity of heavyslugs or BBs at the expense of light slugs or BBs. By using steel BBseach of 1 gram weight interspersed with polyethylene BBs of less than atenth that weight, it has been found that mass adjustments can easily bemade. Under these conditions it has proved advantageous to disperse theheavy BBs among the lighter ones as uniformly as possible.

in the foregoing description of the means for adjusting mass, apresently preferred construction using a tube 52 and BBs or slugs hasbeen described. However, in one alternate construction which has alsoproven useful, heavy liquids such as mercury are introduced into thetube to adjust the mass. Further, while one tube per friction member isordinarily sufficient, plural tubes of various lengths to suit theapplication, are also useful.

From the foregoing description of the preferred embodiments of theinvention, it is apparent that many different embodiments of theinvention may be made without departing from the spirit and scopethereof. Therefore, it is not intended that the invention be limitedexcept as indicated in the appended claims.

What is claimed is: I 1. An improved shaft mounted automatic centrifugalclutch having means for adjusting the engagement speed of said clutchfrom the exterior of said clutch comprising drum means secured to saidshaft for rotation therewith, said drum means having an annular flangewith an access hole therethrough, carrier means mounted within saidannular flange for free rotation about said shaft, arcuate frictionmember means guided by said carrier means and restrained from outwardmotion by spring means, said friction member being positioned interiorof and adapted to frictionally engage said annular flange of said drummeans, and mass adjusting means secured to said friction member, saidmass adjusting means comprising an arcuate tube closed at one end andselectively openable at the other, said selectively openable end beingdisposed to permit its alignment with said access hole, whereby theamount of mass interior of said tube can be varied from the exterior ofsaid clutch.

2. The improved shaft mounted clutch in accord with claim 1 wherein themass interior of said tube is comprised of selected numbers of weights.

3. The improved shaft mounted clutch in accord with claim 2 wherein saidweights are selected from those made of various densities.

4. An improved shaft mounted automatic centrifugal clutch having meansfor adjusting the engagement speed of said clutch, comprising drum meanssecured to said shaft for rotation therewith, said drum means having anannular flange,

carrier means mounted within said annular flange for free rotation aboutsaid shaft,

arcuate friction member means guided by said carrier means andrestrained from outward motion by spring means, said friction memberbeing positioned interior of and adapted to frictionally engage saidannular flange of said drum means, and mass adjusting means secured tosaid friction member, said mass adjusting means comprising an arcuatetube secured to said friction member, said tube being permanently closedat one end and selectively openable at the other, the mass interior ofsaid tube being comprised of selected numbers of weights, said openableend of said tube being disposed on a radius of said friction member andsaid annular flange of said drum means having a hole therethroughlaterally disposed to permit its alignment with said openable end ofsaid tube.

5. An improved shaft mounted clutch in accord with claim 4 wherein saidarcuate friction member means consists of two arcuate friction members,each faced with friction facing material,

said spring means comprises tension spring means,

and

said openable end of said tube means is formed to extend radiallyoutward to terminate at the wear limit of said friction facing material.5

1. An improved shaft mounted automatic centrifugal clutch having meansfor adjusting the engagement speed of said clutch from the exterior ofsaid clutch comprising drum means secured to said shaft for rotationtherewith, said drum means having an annular flange with an access holetherethrough, carrier means mounted within said annular flange for freerotation about said shaft, arcuate friction member means guided by saidcarrier means and restrained from outward moTion by spring means, saidfriction member being positioned interior of and adapted to frictionallyengage said annular flange of said drum means, and mass adjusting meanssecured to said friction member, said mass adjusting means comprising anarcuate tube closed at one end and selectively openable at the other,said selectively openable end being disposed to permit its alignmentwith said access hole, whereby the amount of mass interior of said tubecan be varied from the exterior of said clutch.
 2. The improved shaftmounted clutch in accord with claim 1 wherein the mass interior of saidtube is comprised of selected numbers of weights.
 3. The improved shaftmounted clutch in accord with claim 2 wherein said weights are selectedfrom those made of various densities.
 4. An improved shaft mountedautomatic centrifugal clutch having means for adjusting the engagementspeed of said clutch, comprising drum means secured to said shaft forrotation therewith, said drum means having an annular flange, carriermeans mounted within said annular flange for free rotation about saidshaft, arcuate friction member means guided by said carrier means andrestrained from outward motion by spring means, said friction memberbeing positioned interior of and adapted to frictionally engage saidannular flange of said drum means, and mass adjusting means secured tosaid friction member, said mass adjusting means comprising an arcuatetube secured to said friction member, said tube being permanently closedat one end and selectively openable at the other, the mass interior ofsaid tube being comprised of selected numbers of weights, said openableend of said tube being disposed on a radius of said friction member andsaid annular flange of said drum means having a hole therethroughlaterally disposed to permit its alignment with said openable end ofsaid tube.
 5. An improved shaft mounted clutch in accord with claim 4wherein said arcuate friction member means consists of two arcuatefriction members, each faced with friction facing material, said springmeans comprises tension spring means, and said openable end of said tubemeans is formed to extend radially outward to terminate at the wearlimit of said friction facing material.